How does solo piano help you evaluate audio gear?

Piano has stretched overtones.   I believe it is somehow related to the fact that string has mass.  Extremely long and thin string under extremely high tension would have straight harmonics, but it is not practical.  Because of this stretching piano octave is not tuned to double frequency, but a little bit higher when the beating with overtones of lower octave stops, resulting in about 30 cents error at both ends.  That is why tuning of the piano is so difficult and also why reproduction of the sound is very difficult as well.  Any harmonics produced by the playback system might beat against stretched piano overtones.  Overly warm systems produce even order harmonics that sound great with other instruments or voice, but piano sounds almost like out of tune.

Great post that explain well why piano is so useful for tuning  our system/room...

Thanks very much.....

My deepest respect....

Piano has stretched overtones.   I believe it is somehow related to the fact that string has mass.  Extremely long and thin string under extremely high tension would have straight harmonics, but it is not practical.  Because of this stretching piano octave is not tuned to double frequency, but a little bit higher when the beating with overtones of lower octave stops, resulting in about 30 cents error at both ends.  That is why tuning of the piano is so difficult and also why reproduction of the sound is very difficult as well.  Any harmonics produced by the playback system might beat against stretched piano overtones.  Overly warm systems produce even order harmonics that sound great with other instruments or voice, but piano sounds almost like out of tune.

@mahgister  Thank you.   I read this while ago in Wikipedia.  The title was Piano Tuning.   Opinion about sounding "like out of tune" was expressed by John Siau - technical director of Benchmark.

It becomes really strange when it comes to digital/electric pianos.  Most of them digitize the sound of real piano and because of that have also stretched overtones, but Roland doesn't digitize using complex algorithms to produce piano like sound instead.  Because of that they even allow to choose stretched or non-stretched tuning.  Of course there is no digital piano that sounds like real thing and that alone shows how difficult it is to reproduce piano sound.

@brownsfan  and others, I've been listening to the 1.5 minute piece, "Britten’s Serenade for Tenor, Horn, and Strings."

It's an outstanding test, easy to get to know, and very revealing.

Bought and was a wee bit disappointed with the Moravec Noctures—Pires on DG sound as good and the playing more to my liking. Under the radar and my go to for demo listening and amazing playing is Uchida Live playing Mozart. Two sublime discs from 1992.